A crocodile zoo has said goodbye to one of its "most incredible" inhabitants.

American alligator Albert joined Crocodiles of the World in Brize Norton, Oxfordshire, as an adult in March 2013.

Since then it said he had been a "familiar face beyond the zoo", featuring in television programmes and crocodilian research.

The zoo said in a post on social media on Saturday that after a CT scan, which showed he was "seriously unwell", staff "made the incredibly difficult decision to put him to sleep".

It said he was paired with fellow alligator Daisy, who was also "a long-time resident at Crocodiles of the World and was a star of Channel 5's Croc Man documentary series".

Over the year Albert had fathered many hatchlings and shown "just how gentle, caring and nurturing adult American alligator males can be with their young", the zoo said.

"At over 3m (9.8 ft) long, he was an impressive animal, but he was truly a gentle giant," its post said.

But as he "wasn't quite himself" over the past week, a visit to the vet had been arranged.

"After taking everything into consideration, we made the incredibly difficult decision to put him to sleep," the zoo said.

Its founder Shaun Foggett said called Albert "the most incredible alligator, a big old lovable chap who was so chilled".

"His gentle parenting with his hatchlings was amazing to see, but no real surprise given his nature," he said.

"He will be greatly missed by everyone, especially the keepers, both past and present, who have cared for him over the years."

Crocodiles of the World thanked the alligator "for everything you gave us" and for being "such a special part" of its family.